Last updated: May 20, 2016

There’s a reason your mom warned you not to drink the pool water when you were a kid—and hopefully you listened. A new report from the Centers for Disease Control and Prevention (CDC) found that 78.9% of routine inspections of public swimming facilities identified at least one violation. And one in eight inspections led to immediate closure because of a “serious threat to public health.”

But that doesn’t necessarily mean there was fecal matter in the pool. After the CDC reviewed 2013 data from more than 84,000 pools, hot tubs, and water parks (hello, lazy river!) in five states, they documented the most common violations.

The number one problem cited by inspectors? The water's pH. Maintaining a proper pH is critical for controlling bacteria and preventing outbreaks of gastrointestinal illnesses. Another recent CDC report attributed 69 outbreaks of illness to treated recreational water sources (such as pools and hot tubs) between 2011 and 2012.

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The second most common type of violation was related to safety equipment (think rescue rings and poles) meant to minimize drowning risk.

And the third most frequent issue was the concentration of disinfectant present in the water. The level needs to be precise to keep the water clean without causing side effects, such as eye irritation. And that can be serious business: The CDC points out that health problems associated with pool chemicals (such as burns and breathing difficulties) send thousands of people to the ER each year.

So what can you do to stay safe at your local pool this summer? In a press release, Michele Hlavsa, the chief of the CDC’s Healthy Swimming Program, urges you to look for the facility's inspection results online, and do your own inspection before diving in.

The first step on the CDC's checklist is to test the pH of the water (should be between 7.2 and 7.8) and concentration of free chlorine (at least 1 ppm) or bromine (at least 3 ppm) using test strips that are available at most superstores and pool-supply stores. 

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Next, make sure that you can see the drain in the deep end. That’s a good indicator of the visibility in the water. The clearer it is, the easier it is for others to see you if you need help. 

Also check that the drain covers are secure and in good shape, because a loose or broken cover can trap swimmers underwater, according to the CDC.

And finally, if there’s no lifeguard on duty, locate the rescue ring or pole so you know it’s available, just in case anyone gets into trouble.